The invention relates to a rod coupling as it is used for connecting rod assemblies for underground horizontal boring and trench-less installation or replacing of pipelines (horizontal boring hereinbelow).
In horizontal boring, individual rod assemblies are strung together, connected with each other and moved through the ground by means of a push, pull, or rotary drive. In the case of longer borings, the rod assembly includes multiple rod segments which are, in accordance with the progress of the boring, connected with or separated from each other, one at a time. The individual rod segment is of limited length and must be very short particularly when the boring takes place in a short building pit, for example a hopper, inspection chamber, or man hole. Such hoppers can have diameters of, in part, less than one meter.
Known rod assemblies have couplings of various construction, wherein screw thread couplings are widely used. Aside from the problem that screwing the threaded connections takes a relatively long time and requires clean threads, such connections are particularly disadvantageous in that they allow for rod assembly rotation during the boring progress in one direction only. In the case of, for example, a threaded connection with right-hand thread, rod assembly rotation can only take place in a clockwise direction since otherwise the threaded connection would separate by the boring process.
Therefore, plug-in couplings were developed in the prior art. In contrast to screw couplings, when using plug-in couplings, the problem of fixing the coupling in the coupling mouth after plug-in must be solved since the adhesion-based fixation possibility for the screw thread is not available.
DE 297 13 354 U1 teaches a rod coupling wherein a first coupling part is inserted into a second coupling part. To couple the rod assemblies in accordance with the disclosure of this design patent, the front free end of the first coupling part is pushed, under an angle of about 60° relative to the longitudinal axis of the second coupling part and from the top, into a channel-like receptacle of the second coupling part. Therein, hemispherical protrusions of the first coupling part engage recesses of the second coupling part. From this position, in which the two pipe endings are in an angular relation to each other, the first coupling part is pivoted into the recesses so that the first coupling part reaches the channel-like receptacle of the second coupling part where it is tightly received.
Subsequently, the connection is secured by a safety element in form of a safety sleeve.
DE 196 08 980 C2 and DE 199 18 530 A1 teach rod couplings without the known thread connection and which have at the front end of the rod segment to be coupled an axially protruding lug-like attachment piece that glidingly engages the back end of the preceding rod segment. For this purpose, the face side of the preceding rod segment has an axial slit with a groove into which the lug-like attachment piece can be pushed. Thereby, a journal-like protrusion is brought into a bearing bore of the slit via the groove. By pivoting the subsequent rod segment, the rod segment is moved from the angular plug-in position to the extended position and subsequently positioned in coaxial relation to the preceding rod segment. The axial position is only guaranteed in this position, whereas the lateral fixation is effected by the side walls of the rod segments. Alternatively, the lug-like protrusion is laterally inserted into the slit and then pivoted from the angular plug-in position into the extended position. To ensure that the journal does not fall out of the slit, lateral fixation is provided through protruding side walls of the rod segments, which prevent falling apart of the coupling in the extended position.
DE 100 65 533 A1 describes a coupling in which the rod segments are plugged together. Therein, corresponding ends of the rod segments are connected by parallel-shifting of the rod segment axes, whereby, during parallel-shifting, the rod segments have an angle of a<180° in relation to each other. Thereby, a first rod segment has a journal which engages a corresponding recess of a second rod segment. An undercut prevents the journal from falling out. After rotating in, the undercut engages a shoulder at the subsequent rod segment or prevents falling out through spring-loaded pins that engage a recess in the face side of the end of the subsequent rod segment.
The solutions proposed in the prior art secure the rod segment couplings against radial or axial falling apart by safety sleeves, safety protrusions, spring-loaded pins or by the principle of insertion and removal in an angular position during operation in the extended position.